PB2627: THROMBOTIC THROMBOCYTOPENIC PURPURA, RELAPSE RELATED RISK FACTORS IN A CARE CENTER WITH LIMITED ACCESS TO ADAMTS13 LEVELS.
Authors: Santiago Riviello Goya, Sergio Rodriguez-Rodriguez, Mario Meza-Meza, Juan Luis Ontiveros-Austria, Elena Tuna-Aguilar, Roberta Demichelis-Gomez, Sergio I Inclan-Alarcon, Elia Apodaca-Chavez
Journal: HemaSphere (2023)

Topic: 32. Platelet disorders Background: Thrombotic thrombocytopenic purpura (TTP) is a rare and potentially lethal entity characterized by microangiopathic anemia and thrombocytopenia with severe ADAMTS13 deficiency, with ADAMTS13 auto-antibodies being frequent in patients afflicted by this disease. While low ADAMTS13 concentration is considered the gold standard for diagnosis, clinical suspicion and a high PLASMIC score establishes a tentative diagnosis and justifies initiation of treatment. Mortality has decreased significantly after treatment with plasmapheresis and steroids became the standard of care. After a first episode, approximately one half of patients will relapse. Risk factors such as sex, age and previous episodes are predictive of relapse. Use of rituximab has been postulated as a protective therapy. Aims: The main objective was to describe the epidemiology and management of patients with TTP and identify factors associated with relapses in a low middle income country with limited access to ADAMTS13 measurement. Methods: We conducted a retrospective study of patients with TTP in a Mexican referral center between 1990 and 2021; treatment and follow-up of at least 1 year were required. We established a PLASMIC score ≥6 or ADAMTS13 < 10% as diagnostic for TTP. Data was reported with mean and standard deviation or median and interquartile range (IQR). Overall (OS), relapse-free (RFS), and event-free (EFS) survival (composite of relapse, exacerbation, and/or death) were calculated. Binary logistic regression was used for dichotomous variables, Kaplan-Meier with log-rank and Cox regression was used for survival. Results: A total 69 patients with a median age of 32 (IQR 24-46.5) were included, 61 (88.4%) of whom were women. Fifty patients (73.9%) had PLASMIC score ≥6. ADAMTS13 was measured in 9 cases, all of which were <10%. At presentation, only 3 (4.3%) patients presented with the PTT classical pentad. Forty-eight cases (69.5%) were considered to be primary PTT; regarding secondary causes, 17 (24.6%) were diagnosed with SLE, two (2.9%) with HIV and two with cancer as underlying diseases. Of note, 20 patients tested positive for ANA, 3 of which did not meet SLE criteria. As first-line treatment, 59 (85.8%) patients received steroids and 66 (95.7%) plasmapheresis, the latter with a median of 10.5 (IQR 6.75-20) sessions, which was tapered down in 50 (72.5%) of the patients before discontinuation. Rituximab was used in 13 (18.8%) patients. Eight (11.6%) patients relapsed at least once. In the univariate analysis, the following were identified as protective factors: SLE, use of rituximab, and cerebrovascular event (CVD) at diagnosis, with lupus being significant in the multivariate analysis (OR 0.23, 95% CI 0.06 - 0.98, p = 0.047). Median OS was 206 months, EFS was higher in patients with lupus (126 vs 193 months, p=0.048), sex and rituximab did not show significat differences. The response obtained to plasmapheresis (CR, partial, and no response) significantly affected EFS, and the use of rituximab showed a tendency to improve OS. Summary/Conclusion: Compared to previously described series, this patient population showed a lower relapse rate of PTT, while risk factors for relapse were similar those already identified. A lower relapse rate in lupus patients highlight how in secondary PTT cases treatment of the underlying disease is of utmost relevance. An improved OS in patients treated with rituximab suggests use of this drug might bring survival benefits.Keywords: ADAMTS13, Thrombotic thrombocytopenic purpura (TTP), Coagulation